The amp hartail has great geometry and seems to squat a lot more than previous hartails I have owned but this is great for manueling jumps and soaking up speed when racing. The small size is very small and the wheel base is not too long so for a person 6ft or over the large will be the way to go. The bike is super light and handles great, I have raced it at world cups dirt jumped with it and even put a big post in it and taken it XC riding although not ideal on rides over an hour.
The only recommendation I have is to upgrade the rear axle from a quick release to a bolt on as the drop outs are horizontal and you may need the extra strength of a bolt on.
Great all round bike which is really light and perfect for jumping and cornering and the only downfall is the horizontal dropouts which can be fixed with a simple bolt on rear axle